In a thin film transistor liquid crystal display, an image is displayed by changing the voltage applied to the pixels to vary the field applied to the liquid crystal to control the twisted angle or arrangement of the liquid crystal molecule, thereby to control the luminous flux amount.
FIG. 1 illustrates a schematic diagram of a typical thin film transistor liquid crystal display. The thin film transistor liquid crystal display 100 includes a scan driving circuit 101, a data driving circuit 102, a plurality of scan lines 1021-102m, a plurality of data lines 1011˜101n and a plurality of thin film transistors 103. The scan lines 1021-102m are arranged in parallel. The data lines 1011˜101n are also arranged in parallel and cross the scan lines 1021-102m. The data lines 1011˜101n are insulated from the scan lines 1021-102m. The thin film transistors 103 are located in the positions that the data lines 1011˜101n crossing the scan lines 1021-102m. The gate electrodes of the thin film transistors 103 are coupled to the scan lines 1021-102m respectively. The source electrodes of the thin film transistors 103 are coupled to the data lines 1011˜101n respectively. The drain electrodes of the thin film transistors 103 are coupled to the pixel electrodes 104 respectively.
The top glass substrate includes common electrodes 105 corresponding to the pixel electrodes 104. The material forming the common electrodes 105 is Indium Tin Oxide (ITO). A pixel unit includes a pixel electrode 104, a common electrode 105 and liquid crystal molecules between the pixel electrode 104 and the common electrode 105. A pixel unit is a minimum display unit in a liquid crystal display 100. Typically, a common voltage Vcom is applied to all common electrodes 105 and gray voltages related to the pixel data are applied to corresponding pixel electrodes 104 to generate voltage difference. The liquid crystal molecules between the common electrodes 105 and the pixel electrodes 104 are rotated to special angles by the voltage difference to display gray images.
FIG. 2 illustrates a schematic diagram of a waveform of a signal to drive the thin film transistor liquid crystal display 100. The waveforms G1-Gn are the scan signal waveforms applied to the scan lines 1021-102m respectively, The waveform Vcom is the common voltage waveform applied to the common electrode 105. The waveform Vd is the gray voltage waveform applied to the pixel electrodes 104. Referring to FIG. 1 and FIG. 2, the scan driving circuit 101 generates a plurality scan signals, waveforms G1-Gn, to the scan lines 1021-102m in a frame. The scan signals G1-Gn are high-level signals. When the scan signals G1-Gn are applied to the scan signals G1-Gn, the thin film transistors are turned on by the high-level scan signals G1-Gn. Then, the data driving circuit 102 transfers gray level voltages to the pixel electrodes 104 through the turned-on thin film transistors 103 to make pixel units to shown an image of the frame.
In the foregoing driving method, the frame rate of the display is 60 Hz or 75 Hz. That is, 60 images or 75 images are continuously shown in the display in a second. However, in a case, some continuous images are static images, that is, these images are same images. In other words, it is not necessary to repeated renew the display in this case. Therefore, such unchangeable frame rate will result in invisible waste.